Week 1 - Matter and measurement Flashcards
Broad definition of matter
Broadly defined, matter is anything that has mass and occupies space. Matter exists in three physical states, and classification of matter, in which matter can be identified as element, compounds and mixtures, is of a particular importance in studying properties of matter.
Define substance
A substance is a particular kind of matter with a definite, fixed composition. Sometimes known as pure substances, substances are either elements or compounds.
Difference between homogenous and heterogenous mixtures
Homogeneous matter is uniform in appearance and has the same properties throughout. Matter consisting of two or more physically distinct phases is heterogeneous.
Difference between physical and chemical properties
Physical properties are the inherent characteristics of a substance that can be determined without altering its composition. For example, colour, taste, odour, state of matter density, melting point, and boiling point are physical properties.
Chemical properties describe the ability of a substance to form new substances, either by reaction with other substances or be decomposition.
4 steps to the general scientific method: (OFEM)
Observations, in which facts or data are collected
Formulate a hypothesis that will account for the observation
Experiments to test the hypothesis
Modify the hypothesis and more experiments
Rules for counting significant figures
Nonzero digits. All nonzero digits are significant.
- Exact numbers. Some numbers are exact and have an infinite number of significant figures: 25 dollars, 12 inches in 1 foot, 60 minutes in 1 hour. Exact numbers have no uncertainty.
- Zeros.
a. A zero is significant when it is
—between nonzero digits: 205 has three SF, 61.09 has four SF.
—at the end of a number that includes a decimal point: 0.500 has three SF, 3.00 has three SF, 20. has two SF.
b. A zero is not significant when it is
—before the first nonzero digit. These zeros are used to locate a decimal point: 0.0025 two SF, 0.0108 three SF.
—at the end of a number without a decimal point. Unless specified, 1000 has one SF, 590 has two SF.
Sig Fig rule for multiplication and division
In calculations involving multiplication or division, the answer must contain the same number of significant figures as in the measurement that has the least number of significant figures.
Sig Fig rule for addition and Subtraction
The results of an addition or a subtraction must be expressed to the same precision as the least precise measurement. This means the result must be rounded to the same number of decimal places as the value with the least decimal places. For example:
125.17 + 129 + 52.2 = 306.37
The number with least precision is 129. Therefore, the answer is rounded off to the nearest unit: 306.
Difference between Mass and Weight
In science, we define mass of an object as the amount of matter in the object. Mass is measured on an instrument called a balance. The weight of an object is a measure of the effect of gravity on the object. Weight is determined by using an instrument called a scale, which measures force against a spring.
