UPCAT Chemistry — Matter, Mixtures & MeasurementFlash Cards

What is matter and what are its two main classifications?

Matter is anything that has mass and occupies space (volume). It is classified into two main types: Pure Substances (definite composition and distinct properties) and Mixtures (combination of two or more substances combined physically that can be separated mechanically).

Distinguish between an element and a compound with examples.

Element: composed of the same type of atoms; cannot be broken down by chemical means. Examples: Hydrogen (H), Gold (Au), Silver (Ag). Compound: made of two or more different types of atoms chemically combined; cannot be separated by physical means. Examples: Water (H₂O), Carbon dioxide (CO₂).

What is the difference between homogeneous and heterogeneous mixtures? Give examples.

Homogeneous mixtures are uniform in appearance throughout. Examples: brine (salt water), sugar solution, vinegar. Heterogeneous mixtures are not uniform; components are easily seen. Examples: oil and water, sand and water, salad.

What is the Tyndall Effect and which type of mixture shows it?

The Tyndall Effect is the scattering of light by particles in a mixture. It is shown by colloids - particles too large to dissolve but not large enough to settle. Examples of colloids that show this effect: milk, mayonnaise, butter.

Name and describe three methods for separating mixtures.

1. Filtration: separates liquid from solid using filter paper; filtrate passes through, residue stays. 2. Distillation: separates liquids with different boiling points by heating and condensing. 3. Decantation: separates liquids with different densities by careful pouring.

Compare the properties of solids, liquids, and gases in terms of shape, volume, and compressibility.

Solid: definite shape, definite volume, incompressible. Liquid: indefinite shape (takes container shape), definite volume, compressible. Gas: indefinite shape, indefinite volume (takes container volume), highly compressible.

What happens during sublimation and deposition? Give examples.

Sublimation: direct change from solid to gas without becoming liquid. Example: dry ice (solid CO₂) turning to gas. Deposition: direct change from gas to solid without becoming liquid. Example: frost formation from water vapor.

What is the difference between a physical change and a chemical change?

Physical change: changes form/shape without altering chemical composition. Examples: melting ice, cutting paper. Chemical change: chemical composition is altered; new substance is formed. Examples: burning wood, rusting iron, souring milk.

What happens when sodium metal reacts with water?

2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g). This is a vigorous single replacement reaction that produces sodium hydroxide (a base) and hydrogen gas. The reaction is exothermic and can be dangerous due to the explosive hydrogen gas produced.

Calculate the pH of a solution with [H⁺] = 1.0 × 10⁻³ M.

Using the formula: pH = -log[H⁺]. Step 1: pH = -log(1.0 × 10⁻³). Step 2: pH = -log(1.0) - log(10⁻³). Step 3: pH = 0 - (-3) = 3. Answer: pH = 3 (acidic solution).

If pH = 9, calculate [OH⁻] concentration.

Step 1: pH + pOH = 14, so pOH = 14 - 9 = 5. Step 2: [OH⁻] = 1.00 × 10⁻ᵖᴴ = 1.00 × 10⁻⁵ M. Answer: [OH⁻] = 1.0 × 10⁻⁵ M (basic solution).

Write the neutralization reaction between hydrochloric acid and sodium hydroxide.

HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l). This is an acid-base neutralization reaction where HCl (strong acid) reacts with NaOH (strong base) to produce NaCl (salt) and water. The reaction is exothermic.

State the Law of Definite Composition and give an example.

The Law of Definite Composition states that any given compound contains the same elements in the same proportions by mass. Example: Pure water (H₂O) always contains 11.19% hydrogen and 88.81% oxygen by mass, regardless of its source.

Calculate the density of a substance with mass 25.0 g and volume 10.0 cm³.

Using the formula: ρ = m/V. Step 1: ρ = 25.0 g ÷ 10.0 cm³. Step 2: ρ = 2.50 g/cm³. Answer: The density is 2.50 g/cm³.

What is the difference between endothermic and exothermic reactions?

Endothermic reactions absorb energy from surroundings (+ΔH). Examples: photosynthesis, melting ice, evaporating water. Exothermic reactions release energy to surroundings (−ΔH). Examples: combustion, rusting iron, neutralization reactions.

Distinguish between intensive and extensive properties with examples.

Intensive properties do not depend on quantity of matter. Examples: density, temperature, color, melting point. Extensive properties depend on quantity of matter. Examples: mass, volume, total energy, length.

How many significant figures are in 0.00450 g?

Answer: 3 significant figures. Rule: Zeros to the left of the first non-zero digit are not significant (the first two zeros). The digits 4, 5, and the final 0 are all significant because the final zero is to the right of the decimal point.

Convert 2.5 kg to grams.

Using conversion factor: 1 kg = 1000 g. Step 1: 2.5 kg × (1000 g/1 kg). Step 2: 2.5 × 1000 = 2500 g. Answer: 2500 g or 2.5 × 10³ g.

Convert 25°C to Kelvin and Fahrenheit.

To Kelvin: K = C + 273.15 = 25 + 273.15 = 298.15 K. To Fahrenheit: F = (9/5)C + 32 = (9/5)(25) + 32 = 45 + 32 = 77°F. Answers: 298.15 K and 77°F.

What is plasma and where is it found?

Plasma is the fourth state of matter - a gaseous mixture of positive ions and electrons formed at very high temperatures. Examples: stars (including the Sun), lightning, aurora borealis (Northern Lights), plasma TVs, and laboratory fusion reactors.