1. Translate and memorize the following words.

science	react	matter
crystal	compose	ancient
property	accompany	sufficient
structure	undergo	quantitative
catalysis	develop	external
field	introduce	equal
branch	state	regular
concept	discover	homogeneous
theory	take place	heterogeneous
volume	create	thorough
pressure	deal with	artificial

2. Pay attention to the reading of the following words:

material, magic, quantitatively, undergo, relationship, composition, condition, concept, accompany, molecule, colour, fundamental, among, important, hydrogen, biochemistry, radium, geology, create, origin, machine, manufacture, ceramics, polymer, liquid, century, homogeneous, heterogeneous, alloy.

3. Read the following words and define the parts of speech. Mind the stress:

chemistry – chemist – chemical - chemicals; transform – transformation; nature – natural; practice – practical – practically; understand – understandable; homogeneous – homogenity; equal – equality; external – internal; quantity – quantitatively; regular – regularly – regularity; origin – original – originally; art – artificial – artificially; structure – structural.

Study and remember the following chart:

We attended all the lectures last month.	You did not/didn’t attend last lecture.	Did they attend last lecture?
He gave the lectures in colloidal chemistry that time.	He didn’t give lectures in organic chemistry that time.	Did he give lectures in organic chemistry that time?

Use the Past Simple Tense if an action took place:

• yesterday, last week(month, year, etc.),

• some days(minutes, hours, etc.) ago, the other day, in 2000.

• or didn’t take place that time.

4. Ask the questions according to the model:

Model: He visited our lab yesterday. – Did he visit our lab yesterday?

Who visited our lab yesterday?

When did he visit our lab?

1. He answered all the questions last presentation. 2. We gave you all the information yesterday. 3. They left the Institute some minutes ago. 4. In the 19^th century A. Avogardo introduced the concept of molecules. 5. In 1869 D.I. Mendeleyev systematized elements. 6. I didn’t go to the University last week. 7. Last century A.M. Butlerov introduced the structural theory of organic chemistry.

5. Complete the following sentences according to the model. Use the Past Indefinite Tense:

Model: He studies organic chemistry but last year he studied inorganic chemistry.

1. The students come to the Institute at 9 but last year they ... at half past nine. 2. She carries experiments herself but some time ago she ... them under the teacher's supervision. 3. He works at the Research Institute but two years ago he ... at the plant. 4. They speak English rather well but last year they ... poorly.